Fetal monitoring during labor and birth has become standard procedure in obstetric centers in the United States. Typically during early stages of labor extrauterine ultrasound probes placed on the maternal abdomen derive a signal which when processed yields fetal heart rate and maternal contractions. Subsequently, when labor has advanced to the point that the amniotic membranes have ruptured, the maternal cervix has dilated to 3 cm. and the fetus' head is presented, electrodes that penetrate the scalp are fastened to the fetus' displayed head. The signals picked up by this electrode are directed through multi-component processors yielding fetal heart rate (hereinafter FHR). Comparators in multi-component processors compare current FHR vs. FHR over time as well as a preprogrammed normal current FHR and FHR over time. Some systems have alarms incorporated into the circuits which are preset to alert the obstetric team (hereinafter OBT) that FHR is too high/too low, etc. The thus measured FHR is one of the means of detecting fetal distress. Based on FHR plus ultrasound viewing of the fetus and maternal medical indications the OBT may take other action such as inserting probes through cervical os to measure amniotic fluid pressure and maternal contraction pressure. In some cases, such as prolonged labor or early rupture of the membranes, synthetic amniotic fluid may be infused into the uterus to relieve fetal distress. In other instances the OBT may reach the conclusion that labor should be terminated by cesarian delivery.
In many cesarian deliveries triggered by FHR information it has been found that the fetus was not really in critical distress and could have been vaginally delivered in normal fashion.
One of the shortcomings of the state of the art systems is the variability of FHR which may change quite dramatically during maternal contractions. This information gathered by the sensors attached to the fetus' scalp is processed by multi-processors and is included in the readout of average FHR vs. actual and time line FHR. This processed information may lead the OBT to conclude there is fetal distress. However, this may not be the case, merely FHR slowing because of extracranial pressure caused by the maternal contractions.
Alternatively such processed FHR readings may not show actual fetal distress.